class Solution:
  def upstairs(self, levels: int) -> int:
    res = [1, 2]
    if levels <= 2:
      return res[levels-1]
    for i in range(2, levels+1):
      res.append(res[i-1] + res[i-2])
    for level in range(len(res)):
      print("{}\t{}".format(level, res[level]))
    return res[levels-1]


if __name__ == "__main__":
  solution = Solution()
  print(solution.upstairs(100))
